The present invention relates to a honeycomb adsorbent molded from powdery activated carbon, as an adsorbent used for, for instance, a treatment of fuel vapor of an internal combustion engine of a vehicle, and a method of manufacturing the honeycomb adsorbent, and also relates to a canister having the honeycomb adsorbent.
For instance, for an internal combustion engine of a vehicle, in order to prevent release of fuel vapor evaporated from a fuel tank of the vehicle into the outside, a canister that is capable of adsorbing and desorbing the fuel vapor is provided. The canister temporarily adsorbs the fuel vapor that is generated after a vehicle stop etc., and desorbs an adsorbed fuel component by an air flow during a drive, then the fuel component is burned in the internal combustion engine.
The canister has a casing, a charge port and a purge port which are disposed at one end of a flow passage formed by the casing and also has a drain port which is disposed at the other end of the flow passage. The canister is configured so that during the purge, atmospheric air is introduced into the casing from the drain port.
Here, in recent years, emission requirement (or emission control) has required reduction in a leak of the fuel component that slightly leaks from the drain port as time progresses in a vehicle stop state, i.e. reduction in the leak of so-called bleed emission. As a bleed emission test, for instance, a DBL (Diurnal Breathing Loss) test is provided.
Reduction in an adsorption residual amount on a drain port side in the canister is effective in suppressing. the bleed emission from the drain port.
U.S. Pat. No. 6,540,815 (hereinafter is referred to as “U.S. Pat. No. 6,540,815”) discloses that, in order to reduce the adsorption residual amount on the drain port side, activated carbon whose adsorption capacity (e.g. BWC (Butane Working Capacity)) is low is arranged in an adsorbent chamber on the drain port side in the canister. Further, U.S. Pat. No. 6,540,815 discloses that the canister uses a honeycomb adsorbent formed by extruding activated carbon into a honeycomb shape.
Japanese Unexamined Patent Application No. 2009-019572 (hereinafter is referred to as “JP2009-019572”) discloses that a cross-sectional area of a passage of an adsorbent chamber on a drain port side in a canister is set to be small, and large-grained macroporous activated carbon is arranged in this adsorbent chamber.
Japanese Unexamined Patent Application No. 2005-306710 (hereinafter is referred to as “JP2005-306710”) discloses a configuration using a honeycomb adsorbent as a sub-canister connected to a drain port of a main canister. In particular, in JP2005-306710, by setting a thickness of a partition wall of the honeycomb adsorbent to 0.35 mm or thinner, a rate of a cell opening area becomes large, and a pressure loss is suppressed.